The central objective of the proposed research is to determine the molecular basis for protein-nucleic acid recognition which leads to the proper assembly and stability of simple plant and bacterial viruses. The specific aims are: (i) to determine the secondary structures and conformations of nucleic acid and protein molecules in viruses, (ii) to identify the specific molecular subgroups which are responsible for intermolecular and intramolecular interactions in viruses, and (iii) to identify chemical factors, such as pH, ionic composition and the like, which control the proper assembly and disassembly of viruses. The above aims will be pursued primarily by laser-Raman spectroscopy of mature virions, of precursor particles isolated during plant virus or phage morphogenesis, and of purified capsid, procapsid, tail-spike and DNA-binding proteins. Viruses and viral components will also be investigated by electron microscopy and complementary spectroscopic methods. The interpretation of results on viruses will be aided by parallel studies of model nucleic acids and nucleoproteins. The data of Raman spectroscopy will be collected on a newly constructed and computerized laser Raman spectrometer employing both visible and near-ultraviolet lasers. The viruses targeted for initial study include representative filamentous viruses (fd, Ifl, Ike, Pfl, Xf, Pf3 and Cf), ds DNA viruses (P22 and T7), and RNA plant viruses (TMV and CCMV). The gp5-DNA complex of fd and corresponding complexes involving DNA binding proteins of other filamentous viruses will also be investigated.